But Hyatt, hearing that camphor could be used and not knowing enough
about what others had done to follow their false trails, simply mixed
his camphor and guncotton together without any solvent and put the
mixture in a hot press. The two solids dissolved one another and when
the press was opened there was a clear, solid, homogeneous block
of--what he named--"celluloid." The problem was solved and in the
simplest imaginable way. Tissue paper, that is, cellulose, is treated
with nitric acid in the presence of sulfuric acid. The nitration is not
carried so far as to produce the guncotton used in explosives but only
far enough to make a soluble nitrocellulose or pyroxylin. This is pulped
and mixed with half the quantity of camphor, pressed into cakes and
dried. If this mixture is put into steam-heated molds and subjected to
hydraulic pressure it takes any desired form. The process remains
essentially the same as was worked out by the Hyatt brothers in the
factory they set up in Newark in 1872 and some of their original
machines are still in use.
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